Different techniques are available on the market for detecting events occurring in connection with a fuel dispensing unit and/or a fuel payment terminal. Some events that should be detected are related to the operation of the fuel dispensing unit, such as detecting if a fuel dispensing nozzle is lifted from its nozzle boot, what kind of fuel grade is selected for dispensing etc. Other events are related to misuse of the dispenser, e.g. attempts to steal fuel.
Today, switches that employ magnetic field sensors, push-buttons, etc. are used for detecting certain events. Moreover, it is known that fuel dispensers may incorporate nozzle detecting switches that are capable of performing logical operations. However, at present it is not clear what kind of logic such switches perform.
A problem with switches for fuel dispensing units is that it is hard to use a more common switch design for detecting several different kinds of events, such as lifting a fuel dispensing nozzle, selecting a specific fuel grade, releasing a theft alarm, etc.
In cases of burglary and other tampering for the purpose of stealing fuel, anti-theft systems are used which incorporate some kind of tamper-detecting sensor that breaks a switch which thus gives or breaks a signal between the fuel dispensing unit and a central unit. When this occurs contact is lost between the fuel dispensing unit and the central unit, an alarm is initiated and the fuel dispensing unit is inactivated. Inactivation involves, for instance, setting a logic variable in the control system of the pump at a certain value so that that pumping is not allowed, or, in a mechanical control system, activating a mechanical stop which physically prevents pumping.
U.S. Pat. No. 6,067,476, for example, discloses a technique for protecting a fuel dispenser unit by detecting tampering with a totalizing device acting to keep a running total of fuel dispensed from the fuel dispenser. An electric circuit is included and contains a coil that emits a magnetic pulse that is responsive to a condition consistent with proper totalizer operation. Arrangements are included for sensing the presence of the magnetic pulse, generating a signal responsive thereto and causing an alarm responsive to absence of the magnetic pulse.
A drawback of the above-described anti-theft systems is that they still can relatively easily be tampered with so as to allow theft of fuel. By existing components being bypassed, joined with tape, broken to pieces or replaced with other components, the fuel dispensing unit can be started so that theft of fuel can take place.